Vignette on registering adjacent sections

[lambdamoses]

I already have the code for using the affine transformation matrix from BigWarp (need to take screenshots) and for using point cloud registration in the LOMAR package. The point cloud registration is on the tissue boundary and won't work if the tissue covers the entire study area or for round TMA cores. I also have code for using RNiftyReg though it didn't work for my particular dataset. The existing code transforms the vector geometries to align to a reference. Shouldn't be too hard to transform images as well; EBImage does affine transformation. I won't be able to add support for other image registration methods for 3.19.

Burning question: With expanding features, the SFE package will get more extensive vignettes. Should they be on a separate SFE documentation website built in the same way as the Voyager documentation website, or should they be on the Voyager documentation website? Well, AnnData has its own separate documentation website. But meanwhile I already have the vignette on creating SFE objects on the Voyager website.